Click the "Test" menu to play the swf normally, but the export Gif is a static image

I have a fla file with only 1 frame, click the "Test" menu and the animation plays fine. When exporting the gif, there is only one static image, which seems to be the current frame. How to export gif like swf is a complete animation effect. How to write actionScript。

Figure 1 is a screenshot of playing swf

Figure 2 is the exported Gif static image